The present invention relates to self-propelling agricultural machines, and particularly to harvester threshers.
In self-propelling agricultural machines, traveling mechanisms are usually provided with four wheels, with at least two front wheels which are driven and two rear wheels which are steerable. The growing machine sizes and the associated increasing mass of the agricultural machines however negatively influence the ground compression and traction of the machines. For this reason, the modern self-propelling agricultural machines are provided with all wheel drives to assure sufficient traction. In order to encounter the increasing ground compression, increasingly wide tires are utilized, such as for example so-called "Terra" tires or twin tires.
It is however difficult to provide an optimal balance of harvester thresher with a tire traveling mechanism since on the one hand due to the suspended cutting mechanism, the threshing mechanism and the driver's cabin the center of gravity of the machine is located substantially forwardly. In addition due to the filling of the upwardly located grain tank the center of gravity of the machine is displaced upwardly depending on the filling inside the grain tank can be additionally displaced in the longitudinal or transverse direction. When the harvester thresher operates on slopes, one side of the traveling mechanism must transfer a greater part of the driving and steering forces. During the operation of the harvester thresher, as well as other self-propelling agricultural machines on the slopes, the problem of the balance, traction and ground compression becomes even more substantial.
In particular moist ground conditions, for example during rice harvesting or marshy grounds, the harvester threshers nowadays use short, so-called semi-caterpillars instead of front wheels. Frequently also the complete wheel traveling mechanism is replaced with a full caterpillar system. While the full caterpillars cannot be used because of their high costs, the semi-caterpillar traveling mechanism with semi-caterpillars cannot be further expanded on the forward axle due to the disadvantages which have not been resolved. Traveling comfort and speed are increased with the utilization of rubber running bands instead of the previously utilized steel chains. In particular the steering through the rear axle provided with tires poses problems in difficult bottom conditions. For example the rear wheels can compress the bottom in undesirable manner or due to the insufficient fraction is not in position to transfer the steering force to the ground. For remaining self-propelling agricultural machines, the outer wheel or full caterpillar traveling mechanisms have now concepts for the traveling mechanism which improve the traction or reduce the ground compression.
It is known to use for tractors or military vehicles a traveling mechanism with a half caterpillar forwardly and two half caterpillars rearwardly as disclosed for example in the German patent documents DE 461466, DE 593303, DE 3511647 and the U.S. Pat. No. 4,729,445. This traveling mechanism concept is however not suitable for harvester threshers and other self-propelling agricultural machines, since the conventional weight distribution does not allow the utilization of only one forward caterpillar. The German document DE 309030 discloses a traveling mechanism concept with four semi-caterpillars, in which the rear side caterpillars are steered. This approach is however expensive to manufacture because of the use of four semi-caterpillars. The prior art discloses no suggestion where and how to arrange the hinged semi-caterpillars behind in the self-propelling agricultural machine.